High blood pressure before pregnancy tied to increased risk of miscarriage

Women who have high blood pressure (hypertension) before they get pregnant may have an increased risk of miscarriage, even if they don’t have a diagnosis. That’s the conclusion of a study published in the American Heart Association’s journal Hypertension.

The researchers studied more than 1,200 women who had already experienced pregnancy loss, and who were trying to become pregnant again. Their blood pressure was measured in the first observed menstrual cycle (before conception), and again during early pregnancy.

Of the 797 participants who conceived within six months, 24 percent suffered another miscarriage.

The women’s blood pressure before conception did not affect their fecundability (the probability of conception). However, every 10-point increase in diastolic blood pressure (see below) was associated with an 18 percent increased risk of miscarriage.

Enrique F. Schisterman, Ph.D., senior author of the study, said:

The impact of cardiovascular risk factors starts really early in life. Physicians treating women of reproductive age should pay attention to slightly elevated blood pressure because it may have other not-well-recognized effects, such as adverse pregnancy outcome.

The participants were part of a clinical trial seeking to determine if low-dose aspirin might reduce the risk of miscarriage. The researchers found that it made no difference to the impact of blood pressure on pregnancy whether the women had taken aspirin or not.

Since all the participants in the study had already experienced at least one miscarriage, it’s unclear whether the results can be generalized to all women. However, elevated blood pressure can damage your health in multiple ways, and getting it under control is always a good idea.

How can you know if you are at risk?

Most people with hypertension don’t feel any symptoms. The only way to find out if you suffer from high blood pressure is to have it tested. You can easily get your blood pressure checked at your doctor’s office; many doctors do it routinely at every appointment.

You can also buy a home blood pressure monitor and measure your blood pressure yourself. To make sure your readings are accurate, follow the instructions carefully. Avoid tobacco, caffeine, stress, and anxiety before measuring, since these factors can cause your blood pressure to rise.

Blood pressure readings have two numbers, for example 115/85 mmHg (read as “115 over 85”):

  • The first number is your systolic blood pressure (the highest pressure when your heart beats).
  • The second is your diastolic blood pressure (the lowest pressure when your heart rests between beats.)

Systolic blood pressure typically receives more attention. In the study mentioned above, however, it was elevated diastolic blood pressure that was associated with higher miscarriage rates.

The American Heart Association considers a normal blood pressure reading as 120/80 mmHg or less. You can find a chart showing healthy and unhealthy blood pressure ranges here.

If you measure your blood pressure yourself and get an unexpectedly high number, don’t be alarmed. It might well be a one-off and nothing to worry about. Try to calm down, and measure again at another time.

If you find that your readings are consistently high, however, see your doctor to discuss your condition.

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